Unfolding of Morning Glory Flower as a Deployable Structure

Abstract

Although there are some plant leaves which just grow from small size to normal size, most leaves or flowers not only grow but also deploy or unfold from their small buds. In the buds of leaves or flowers, therefore, various ideas to stow their bodies such as folding or rolling are often observed. For example, the leaves of hornbeam or common beech have a typical corrugated folding pattern [1,2] while the fan-type bellows pattern is observed in maple leaves [3]. As well-known, the petals or petal ribs of a morning glory flower mysteriously spiral in a bud. Beetles or grasshoppers have also folding patterns in thin hind wings under hard covering fore-wings which have been studied by many researchers [4–7]. The movements of beetle wings folding at rest were investigated and compared with those in flight [8]. In recent works[9,10], it was indicated that the key folding/unfolding system adopted in the hind wings of Coleopetra consists of four folding lines intersecting in a point. A number of deployable structures observed in nature are summarized and classified by Kresling [11]. The investigation of the folding/unfolding manner in plants [12] and insects, may be useful for in designing some artificial deployable structures [13–15], such as solar panels, antenna of satellites, or deployable roofs. However, there are little research concerning folding patterns in nature from mechanical point of view.